Your Best Magician, Marisa
by Jain vi Bookshelvia
Summary: King Asgore was conflicted; his son's new mentor was exceptional, imparting insights that even he did not know. With it came the realization that the Crown Prince had grown a habit of firing lasers that left spots in his eyes. Prequel to Undertale / Crossover with Touhou Project. Mentor!Marisa. Image by xmichiyo
1. Once Upon an Orient Time

Having spent all of her life within Gensokyo, Marisa Kirisame never realized how small her world was.

Now, here she was, outside the Great Hakurei Barrier, did she know.

The view above Mt. Ebott was breathtaking, watching the sun setting in the distance in a great orange-red blaze. The hue covered the mountainside, cascading its cragged face in its radiance. Valleys caught between were eclipsed in shadow, blanked utterly into inky rivers of black.

Suddenly, the witch felt a stockpile of magic building, erupting into a bright flare.

Marisa grinned and descended down towards it.

She leapt off her broom, landing with a loud thump and kicked up a small dust cloud. With a flick of her wrist, the broom flew back into her hands and shimmered. The blonde magician twirled it deftly, blowing away the lingering puffs in the air.

A figure walked out of the settling debris, his blonde mane and beard shook as he coughed into a white furred fist. Marisa stared the sight of an anthromorphic goat man, towering several heads over her. Two large, curving horns grew from his temples into a magnificent arc around a small golden crown. He wore a regal blue cape over a stylized purple and white dress robe, bearing a stylized crest that caught her eye.

"That there's the Delta Rune, right?" Marisa extended a smudged hand, paused to wipe it on her apron and reoffered it out. "So that means you're part of the Royal Family 'round these parts. I'm Kirisame Marisa."

"Well met, Kirisame," he greeted. "I am King Asgore Dreemurr, Ruler of the Underworld. We hope you enjoy your stay here with us."

"I do too," Marisa cheekily replied. "I plan on doing more than just sightseeing. Oh, and call me Marisa. Never like formality all that much."

"Then I insist you refer to me as Asgore." The king turned about, gesturing the witch to follow behind. "Miss Patchouli spoke well of you, Miss Marisa. You must be quite the accomplished mage to be held in such esteem, even if begrudgingly."

"Bah, she's just bitter because I'm borrowing a few books from her." Marisa said, palming the side of the cave entrance the two were now entering. "It's no big deal, she can have them all back in one go."

"Oh?" Asgore asked; a thick bush brow rose at that.

"Yeah, not like I can do much with while dead."

"Ahaha!" the King of Monsters bellowed. "Indeed."

After a few twists and turns, the cave's appearance changed from more natural looking formations into one manmade. It was now a straight line, the walls beginning to thrum with an archaic energy. It was familiar somehow, memories of incidents coming to mind as they walked on.

"Say, this stuff's giving off some nostalgic vibes," Marisa wondered aloud. "It kind of reminds me of the Former Hell and Makai."

"You're certainly well-traveled," Asgore chuckled, his deep voice further amplified by the long and narrow hallway. "Yes, the architecture was crafted by artisans of the Esoterica Province in Makai. My ancestors commissioned them to build the infrastructure of our beloved kingdom."

"Bet you've got lots of stain glass in your palace then."

He humored her with a knowing smile.

"I'll take that as a yes," Marisa smirked. "Well, since you've heard so much about me, mind giving the heads up as to what I'm in for? All Patchouli said was something about instructing basic magic."

"Yes, it'd be prudent to resolve of that ignorance," Asgore nodded. "I had asked Miss Knowledge to come and tutor my son and heir the fundamentals of the magic arts. Both the Queen and I were taught by her great-grandfather and we thought to carry on this tradition."

"Ah, I see where you're going with this," the blonde witch interrupted. "Patchy's kinda too frail for this kind of stuff. Asthma and anemia's not a forgiving combo."

"We were initially disappointed to hear this, but she had promised us a proxy in her place. She swore the Magician's Oath that she'd do so and we knew then we could rest easy."

Marisa whistled lowly. That must've been some honor at stake. "So who's the munchkin I'm training into a badass?"

"His name is Asriel," Asgore said, voice brimming with pride. His already straight stance stood even taller at the mention.

"What's he like?"

Marisa resigned herself when she saw that glint in the goat-man's eye, that same glint that appeared whenever a proud parent blathers on about their child.

If that bedridden magician was scrying on her, she was going to tell Aya about that hidden cache in the subbasement.

As devious as she was, nothing was as ruthless as the tabloids.


	2. Unnecessary Tension

Marisa had learned two things about her new employer.

Asgore was every bit the benevolent ruler his presence projected. As they entered the city, he was greeted and welcomed by literally every passerby. The joy in the eyes of his citizens reflected in his own, spreading good cheer wherever he went. That made her respect for him rise.

He was also terrible at names. New Home? _Really?_

His wife, Toriel, was a lovely woman. She was of the same species with a more curvaceous body than her burly husband. She wore matching dress robes, hers a light blue with the Delta Runes inscribed around her bust. Diminutive horns poked out of her head, little nubs compared to the rack Asgore had.

It was then that Marisa realized that Asriel was a combination of his parents' names.

She didn't know whether to find that endearing or nauseating. Either or, her respect for Asgore slowly declined.

According to the guardsmen, the young Prince was out playing with his sister in their front yard. She said her goodbyes to the Queen as the King led her through what he called a shortcut.

Asgore didn't need to turn around to know how smug Marisa was when they arrived at the chapel.

After several another long passageway and a few flights of stairs, the human magician gasped at the remarkably cozy home for a Royal Family. It was surprisingly modest and tidy, for where two young children lived. The walls were a soft green, adorned with pictures and portraits of yellow flowers. The air was heavy with the scent of baked goods. It was butterscotch, judging by the syrupy sweetness, with a dash of cinnamon. She closed her eyes and took a deep whiff, savoring the aroma.

Marisa was shaken out of her trance when she heard Asgore's deep chuckle.

"My Tori's cooking is something extraordinary, isn't it?" He said as he opened the door for her. "Come now, I'm sure she'll be back soon. Delegations end quickly when the Queen takes charge."

Golden gazed upon two children. One was human with a peach complexion and medium-length brown hair, blushing adorably as she ran across the grass. She wore a green and yellow striped shirt with navy blue slacks. While her smile was wide and eyes were crinkled, there was something about it that felt off putting. It reminded her a bit of the younger Komeiji sister without her inherent good nature.

The second one dashed away from the little girl, this one presumably Asriel. He was the same as his father and mother; an anthromorphic goat boy wearing a similar striped shirt with the colors inverted. A tuft of white wagged atop the seat of his pants as he continued to run away. The girl leapt at him, pushing them down together into a pile of fallen leaves.

Marisa smiled at the giggling mess as they splashed each other with crumbled bits of dead leaves. "So that's them, huh?"

Asgore's smile grew even warmer as he held his arms out, "Children, could you please come over here for a moment?"

They paused in their fun, looking to their father before leaping out. Hurriedly brushing off any clinging foliage, they rushed out and grabbed at Asgore's legs. The King leaned down and rubbed at the top of their heads, nuzzling them both in an enveloping hug. He then put them down before gesturing the guest besides him.

"Miss Marisa, I'd like for you to meet my two children, Asriel," the boy huddled behind his father when the blonde witch looked at him, "and Chara."

The girl tilted her head, meeting her with inquisitive eyes. They made her uneasy, with that vacant smile. It was far too hollow to be genuine. Chara gave her a charming grin and the witch returned it as best as she could, her innards nauseous as she held the expression.

"Asriel," Asgore stroked the back of his son's head. "Starting tomorrow, you're going to begin learning magic from Miss Marisa. I expect for you to follow her instructions at all times, do you understand?"

"Yes, Dad," the boy said. He flushed as his father scratched at that spot behind his right ear, reluctantly leaning into the touch.

"Good," Asgore stood up and stepped back. "I'm afraid we'll have to continue this another time, Miss Marisa. The duties of a monarch are ever demanding."

"See you later then," she tilted her hat at the King.

Asgore turned to his children once more. "Please show Miss Marisa to the Guest Room and be good for her, alright?"

The King's body began to glow brightly, light enveloping his entire form. Marisa stared at the spectacle, watching Asgore vanish in a flurry of flames. She'd seen this before, during the Underground Geyser incident.

"Huh. That's an interesting variant of astral projection," she muttered to herself. "Nice touch with the fire."


	3. Anticipation

Marisa leaned back into her wooden chair, huffing as she patted her stomach. "Hoo, that was _great."_

Escargot on the first night? She could get used to this.

Toriel beamed at the praise. "I'm glad you enjoyed it. Snails are a favorite of mine." The Queen sliced open her butterscotch pie, the smell growing more intense as steam wafted out. She handed a plate to Marisa, whose mouth's edges dripped with excess drool.

"It really showed," the magician said absentmindedly, already scooping a piece into her lips. Pastry met palate and Marisa moaned at the taste.

"Miss Marisa," Asgore began, "I did not have the chance to ask what field you specialized in. Would you please inform us?"

"Oh, I guess I never did," Marisa muttered. She saw how everyone's attention focused on her and cleared her throat. "Well, I'm not really like Patchouli. She's got more knowledge than I do since she's older, but I think I've got a better first-hand experience. Being able to get out of the house would do that. Anyways, my magic is more heat and light based, which is good since I'm assuming Asriel's gonna grow into fire."

"Yes," the King nodded, "the royal bloodline is mainly fire attributed, with some exceptions."

"I can tell," Marisa smirked. "Fire magic leaves a very distinct bitter aftertaste in cooking."

"You mentioned earlier that you were younger than Miss Knowledge?" Toriel asked, sitting down into her chair. "I recall her being roughly a century old, relatively young for a magician. Surely, the gap must be inconsequential."

"I guess you could say that," Marisa said between bites. "I mean, I've beaten Patchy before. She's strong, yeah, but she's got a hard time being consistent."

"You've fought Miss Knowledge?" Asgore blinked. "How curious; in what circumstances did you two engage in combat?"

"Hm," Marisa furrowed her brow, putting down her spoon to cup her chin in thought. "Think the first time around was during the Scarlet Mist incident. You know about her current entourage?" Both Asgore and Toriel shook their heads. "She's living with a vampire by the name of Remilia Scarlet. Remilia decided that she wanted to be out and about during the daytime, so she casted this thick blanket of fog into the sky and blocked out the sun for about three days. In Gensokyo, my best friend and I are the big problem solvers. We dealt with Fangs and her mansion of misfits, including Patchouli."

"My," Toriel said slowly. "You must lead quite the exciting life."

"To be honest, that incident was probably one of the tamer ones," Marisa went on. "Right after was the Never-Ending Winter, and then the Fake Moon," she mumbled off, counting on her fingers. "But yeah, Gensokyo's never boring. I've got a reputation for doing this kind of stuff. Champion of the humans, protector of the peace and all that comes with it."

The King and Queen mulled over what she said as Asriel and Chara exchanged confused looks.

"Miss Marisa," Asgore asked, almost hesitant to voice his thoughts. "If I may, why is a magician defending the behalf of humans?"

"Well, that's because I am one."

A collective gasp came from nearly everyone at the table. Asgore and Toriel went still, Chara's eyes widened to the size of saucers while Asriel looked at her with a newfound adoration.

"But," Asgore stammered. "You said you were a magician! Like Miss Knowledge!"

"No," Marisa waved her hand, dismissing that claim. "I said I was a magician as in 'that's my job'. I'm a _human_ magician."

"Cool!" Asriel cried out, leaping off his seat. "I never knew humans could do magic! Does that mean Chara can do it, too?"

The witch felt a shiver going down her spine as Chara's eyes twinkled with an intense hunger. "Maybe? Not all humans can do magic, but some can. We'll find out tomorrow, alright?"

Her gut wrenched when she recognized that expression on the little girl's face. She knew it all too well, having seen it on countless others, including herself.

It was a look of determination.


	4. A Tale of Two Barriers

Marisa sat with the king and queen in their living room, sipping on a cup of what they called 'Golden Flower Tea'. The home was now quiet, Asriel and Chara been put to sleep.

The witch sighed, "Alright, something's been bothering me for a while and I gotta know the answer." She looked to Asgore, who was astonished at the sudden break in silence. "How exactly did you do that earlier?"

Asgore blinked at the question. "I'm sorry; I did not understand the question."

"Back up on the mountain," Marisa explained, settling down her teacup onto its saucer. "You were able to come and escort me down here. On the way, through the long corridor, I detected sealing magic. And not just any conventional stuff either, this kind of barrier is what separates worlds." She crossed her arms, giving Asgore a knowing look. "I know my barriers. I've been living in one for my entire life and my best friend's specialty involves this exact magic. This was cast by a really powerful priest, a _human_ priest. Monsters like you shouldn't be able to interact with it. So how did you cross over?"

"That is most impressive," Asgore admitted. "You must be truly dedicated to your craft if you were able to deduce this much in so little time. Yes, you are correct. There is a barrier that covers this entire land. A great war was waged between our people and the humans. While we fought valiantly, the humans displayed a guile that eventually overwhelmed us. We were defeated, forced underground and never to return to the surface again. However, as mighty as the Barrier is, its creation was relatively recent.

Magic, as you know, only grows stronger as time progresses. My ancestors had allied with the Knowledge Clan for centuries, long before the Barrier was constructed. Our bond of sworn allegiance transcends this, allowing certain privileges under the correct circumstances. While I, in person, may not able to leave, I was able to create a proxy that could. Thus, I was able to escort you into our kingdom."

"You, too, are affected by this," Toriel said, "as the representative of Miss Knowledge; you should be able to cross the Barrier at any time. Its intention was to keep monsters like us within, thus this loophole. In fact, young Chara was the first human to appear in the Underground. Asriel found her in the ruins outside the city and we took her in as our own."

"Well, that answers the second question I had," Marisa leaned back into the comfortable couch. "I'm surprised, though, that you two did. I mean, how did everyone react to this? There should still be some bitterness after that war and I know there's someone out there looking for a scapegoat to blame. The Royal Family adopting a human child must've been like a lightning rod of hate."

"There was some initial disapproval," Asgore lamented, resting his cup down, "but they had grown to love Chara as much as they loved Asriel. Despite our recent loss, our kingdom's future is looking to be bright in those two. Hope, after all, is something that a king must provide for his people."

Toriel stroked her husband's arm, white furred hands interlocking as they exchanged loving eyes.

Marisa rolled her eyes at the display of affection. She silently stood up as the two nuzzled one another, murmuring content hums as they did so.

Just before she reached the hallway that lead to the guest room, the witch stopped.

'Did she really just call him _Fluffybuns?_ '


	5. Wishing Upon a Fallen Star

"So," Marisa began, "you two ready for your first lesson?"

Asriel and Chara nodded frantically, the boy's ears flopping with the motion. They sat in Toriel's study while the witch scribbled onto the enchanted chalkboard she had found in the room.

It was a pleasant surprise at first, and then it became clear when she discovered an entire curriculum for the children of almost everything non-magical. The schedule she found was almost indecipherable, with several cross-outs and hastily written in edits. It was flattering, Marisa thought, that Toriel believed in her enough to cover such a broad spectrum.

"Alright," Marisa said, turning around to meet her students. "You're going to memorize this stuff even if I've got to force it down your throat, Got it?"

Behind her, it read; "Magic is alive and everywhere, in the Largest and Smallest forms possible.

Magic and Science are one and the same; only following a different set of Rules.

Magic is only as finite as its intention and caster. Thoughts and Beliefs shape the World.

Cause and Effect; Always Ask Why."

As the two stared, Marisa pulled a thin piece of wood out the side of the chalkboard. It was sleek and long, around the length of her arm. She stood to the side and gently tapped the top of chalkboard. When the tip touched the first row, the words glowed softly and slowly lifted themselves off the black surface, words hovering in the air in bigger and bolder text.

"This is pretty straightforward," Marisa lectured, "Magic is any and everywhere, thriving as long as its people are. For example, the citizens in the Underground co-exist with magic, some using it in their daily lives. With how the majority of a monster's bodily composition is made of condensed magic, they are more prone to access their magical core than the mundane races. This does not mean they are more powerful, just that the monsters have an easier time. Any life form is capable of magic. This is due to that Life if a magic in of itself. Life bestows self-awareness, consciousness and is acknowledged as the most potent and scarce magic there is. We'll be discussing that later.

"Despite what the surface thinks, magic and science are one and the same. Most humans have forgotten magic in favor of the technological advances they've made, with only a few that practice the old arts." She said, now pointing on the second row. The first receded back into the chalkboard while the letters below flew out in the same fashion. "You've tasted some of what they've got; phones, TVs and all these fancy gadgets? That's all human ingenuity. It's also humanity's newest source of magic.

"Electricity is actually a form of harnessed magic. It's not as concentrated as its other forms, but it suits what humans need it as: energy. Without this energy, the surface would be a completely different place than it is now."

She swung at the third and fourth rows in a tap-tap-swish, both rising at the same time. "These are interrelated, so I'll explain this all in one go. All forms of energy are magic, all of them with a wide variety of names and properties. Electricity is quick to consume, especially with how humans are accustomed to using it. They have these things called 'scientific laws'. They're published details about how the world around them works and are taken as fact. While they're not wrong, they're not completely right either.

"A scientific law is always applied under the same conditions, and implies that there is a causal relationship involving its elements. Normally, these laws are always true and should be considered as such. Take this, for instance…" she pulled a random book from a shelf to her side. "Gravity is the force that attracts a body toward the center of the earth, or toward any other physical body having mass." She tossed the book into air, making a brief arc before landing on the floor with a thud. "It happened and you know why. But what if, one day, you dropped the book and it decided to do this?"

The book rose from the floor, rising all the way up until it hit ceiling. "Then, you ask yourself, 'why did this happen? What made the book go up instead of down? Is this going to happen again? Will it go in any other direction?'" The floating words vanished completely as Marisa put the wooden piece back into its slot on the side of the chalkboard. "A researcher, magical or otherwise, will make observations. If it can be observed, it can be understood. If it can be understood, it can be _controlled_.

"That's how the old and whimsical magic died, replaced by the cold, calculated logic that is everywhere above. Thoughts and beliefs shape the world; I want you to take that very literally."

Marisa laughed, each of them had a different reaction; Asriel simply dropped his jaw, two cute little fangs poked out from beneath his lip while Chara took notes as best she could, her face flushed red at the strain.

"Alright, I'm sure you two wanna get to the hands-on part of the lesson already." She was met with eager nods. "Hold out your hands."

Marisa knelt before them and placed her palms in theirs. The children gasped as they felt something run down their arms and into their chests. Looking down, both of them watched as something erupted from their chests. It was crystalline, the edges and surfaces smooth like a well cut jewel. It resembled a five-pointed star, twinkling merrily in bright yellow bursts as it hovered before their respective owners.

"This spell's a nifty little trick called Crystal Beacon," Marisa explained, watching as Asriel stroked the side of his gem while Chara stared into hers. "It's made up of my magic as its shell. Once I dispel that, you're going to try and pump the gem back into life. With only a fragment of your magic in there, it won't stay lit like that for long. If it helps, picture a cup. That gem is the cup. Then, try and imagine water flowing into that cup. Magic's fluid and prefers to be given a general direction, so make sure you guide it, not force it."

They nodded and tighten their hold onto their gems. With a snap of her fingers, the yellows on their gems vanished. Asriel's gem became a gentle green, verdant and radiant. It emitted pulses of excitement, mirroring its owner's joy. Chara's had changed into a simmering red, flickering between a lighter hue and darker shade every few seconds. It felt pale, somehow, only reflecting the brilliance off of her brother's gem, like the moon and sun.

"Very good," Marisa said. "Now hold it like that a little while longer." She doubted either heard her. Both of them were enraptured by their gems, gazing deeply into their respective cores. Suddenly, the red star began to dim. Chara panicked, squeezing the crystal tautly with both hands. The girl bit her lip, arms trembling as the edges dug into her palms. Soon after, the only remaining color left were the bits tinged lightly with blood. The gem was completely dyed in dull grey, inert and lifeless.

Chara sniffed audibly, her chocolate brown eyes tearing as her lips trembled. Asriel turned his head at the sound, snapping out of his trance and giving his sister a concerned look. He pleaded with Marisa wordlessly and she gave him a resigned sigh. Taking the bloody gem out of her hands and into her apron, the witch stood up pulled Chara away to a corner. The prince stared helplessly as they moved away, dejectedly rubbing at his still shining star.

"Hey munchkin," Marisa whispered, grabbing Chara and pulling her into her lap. "Listen, what happened was actually expected. I probably should've told you earlier, but most humans like us don't have any inherent magical ability. You're not gonna be able to magic like your brother…" The little girl cried out softly at that, tears falling from her downhearted face. "Wait, I wasn't done! This just means you'll have to learn a different kind of magic."

The whimpering stopped along with her breath, almost hesitant to let it out. Watery brown eyes looked back up, hopeful and begging.

"That's right," Marisa continued, "I thought you were listening; most humans don't have any inherent magical ability. In fact, I don't have it either." Chara's eyes widened, tilting her head with a slack-jaw motion. "Yeah, you're probably thinking, 'then how did she do all that stuff? Were the smokes and mirrors?' or something like that. No, it's still magic. For us humans, we can't generate magic, so we get it from another source. Clerics and priests have their patron gods, scientist use electricity and as for me?" She grinned, "Think I'll keep that a secret for now. But you're going to start a more traditional path. One, if you really take to heart, that will carry you into greatness."

She lifted her hand into the air and a book gently floated down from the ceiling. Chara's eyes widened when she realized it was the same tome from earlier.

Its cover read, "A Beginner's Guide to Runes and Calligraphy."


	6. Enemy Approaching

Marisa appraised the handful of armored soldiers standing before her in the palace courtyard, their shoulders stiff and backs straight. They all looked vaguely humanoid, with the occasional tail or fur. She narrowed her eyes, strolling down before each and every one of them. Looking over her shoulder, Marisa asked in a droll tone, "So it has to be one out this lot?"

Asgore nodded, "only they had volunteered for the task at hand, all of them exceptional combatants in their own rights. Worry not; I know they shall perform admirably."

The witch turned back around, giving them all another thorough glance. With all the armor in place, she was having trouble gauging their worth. She wanted someone who sought constant self-improvement, unsatisfied with their present self and courageous enough to pursue an ambitious dream.

Marisa wanted a _fighter._

Both she and Asgore had agreed that she needed to establish her credentials. Her authority had to be respected to be an adequate teacher and any doubts about her capability must be dispelled.

With an exhibition duel, she would do just that.

Something caught her attention; the figure was tall, imposing and lean. The helmet was unusual, the mouth guard jagged and curved, bearing the visage of a wicked grin. Vivid red hair trailed down the back, tied into a single ponytail. In their hands was a spear, the tip gleaming with a handsome polish. However, what truly interested her was the eye she saw peering back from inside.

It was yellow with a vertical slit as the pupil, but it held a ferocity that made the ends of her lips curl upward. There was a kinship there, the anticipation of meeting a worthy adversary that sent tingles at the back of her mind.

Oh yes, this will do.

Marisa came before them, tilting her head back to look up and cheekily said, "Take the tin can off your head."

Metal clad arms reached behind, undoing a clasp before pulling the helmet off.

The first thing Marisa noted was the amount of blue. Then she noticed the teeth. Webbed fins around the fish-woman's head twitched as she stared her down, flashing her mouth of daggers in a taunting manner.

The witch turned around, giving Asgore a thumbs-up. The king smiled indulgently, "Thank you, everyone. You're dismissed; Undyne, stay with us please."

Clinks and clanks cluttered the courtyard, the soldiers leaving in a disorganized fashion. The witch snorted when she saw the King subtly shake his head. He pinched the bridge of his snout ruefully. "All I ask is for a little discipline to show off to our guest. Is that too much to ask?"

"You called them in on a Friday, Your Highness," the fish-woman said, her voice gruff and deep. "Remember? You instated the rule a while ago."

"How could I forget?" He fluttered open his robe, showing his 'Mr. Dad Guy' shirt beneath. "Some decorum is still to be expected, nevertheless."

Asgore gestured to his subordinate. "Miss Marisa, this is my future captain of the Royal Guard and my own protégé, Undyne. Undyne, this is Kirisame Marisa, my son's mentor in the magic arts."

The magician extended her hand, "Call me Marisa."

She was met with a firm grip and squeeze, the metal pinching slightly at her skin. "So you're what His Highness wants beaten into the ground, huh?"

Her cheeks were starting to hurt from holding back the manic grin that wanted to burst forth. "Keep on talkin', Fishy. I wanna cover up that hole you're digging yourself into."

"Now, now," Asgore held up his hand in a placating manner, "There's a time and place for this."

He was promptly ignored in favor of a leering match. Marisa bit the inside of her cheek as they gauged one another, proverbial sparks going off.

And if there was enough room for collateral, more literal Sparks too.


End file.
